System and Method for Computer-Aided Surgical Navigation Implementing 3D Scans

ABSTRACT

A surgical navigation system for providing computer-aided surgery. The surgical navigation system includes a handheld surgical tool with computer-aided navigation, a graphical user interface module, and optionally an imaging device. The handheld surgical tool includes a handle that may comprise at least one sensor for detecting orientation of the. A computing device and at least one display device are associated with the handheld surgical tool and configured to display a target trajectory of the handheld surgical tool for the surgical procedure.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application in a continuation of International Application No.PCT/IB2020/000867 entitled “System and Method for Computer-AidedSurgical Navigation Implementing 3D Scans,” filed Oct. 28, 2020, whichclaims the benefit of priority to U.S. Provisional Application No.62/926,657, filed on Oct. 28, 2019, both of which are incorporated byreference.

FIELD OF THE INVENTION

The invention relates to a surgical navigation system having a handheldsurgical tool with computer-aided navigation. The handheld surgical toolcomprises a housing, an instrument shaft, and a sensor unit. Thesurgical navigation system further comprises at least one imaging unitconfigured to generate a three-dimensional model/contour of ananatomical surface and a graphical user interface module configured todisplay the three-dimensional surface/contour and the location of thehandheld surgical tool.

BACKGROUND

Orthopedic implantation procedures such as hip arthroplasty, kneearthroplasty, shoulder arthroplasty (TSA), and spine arthroplasty, cancomprise two primary steps: a registration step, in which for the boneof interest the virtual frame of reference (for example, as provided bya camera) is matched with the actual frame of reference; and an implanttargeting/placement step, in which the implant device is implanted intothe patient. Proper positioning of surgical tools and implants, withrespect to a patient's anatomy, is extremely important in order toensure the best outcome. For example, in these implantation procedures,proper orientation of surgical guides, cutting tools, and implants isessential to ensure joint replacement functionality. Misalignment of thesurgical guides, cutting tools, and/or implants can lead to detrimentalconsequences, such as joint dislocation, decreased joint motion andmobility, damage to surrounding tissue, long term pain, and earlyimplant failure. For hip arthroplasty in particular, correct implantpositioning may be challenging due to a variety of issues, as alteredanatomy in revision cases, glenoid bone loss, and unreliable landmarksare commonly encountered in the patient population. In these cases,directing the glenoid baseplate along an appropriate axis withsufficient bone stock may be a difficult intra-operative task.

The ability to properly place the surgical guides, cutting tools, andimplants is often difficult for surgeons, and even minor orientationchanges can lead to improper implant alignment. Physical landmarks maybe attached to the anatomy to guide and orient the surgeon during theseprocedures. However, such methods are imperfect and can lead tomisalignment due to various reasons, such as there was an error inregistering the position of the marker relative to the position of thebone; the marker is not secure and moves relative to the bone; or thecamera is unable to detect the marker because of the presence of fluidor material from the surgery that can cover the marker. In instanceswhen the surgeon does not attach markers but rather uses other physicalfeatures of the body for registration, errors can occur if thosephysical features are inaccurately measured or if the surgeon does notorient the patient's anatomy properly. And while three-dimensionalreconstructions of computed tomography (CT) or magnetic resonanceimaging (MRI) scans can improve surgical planning, recreating the sameplan during surgery can be a demanding task.

In order to attempt to address at least some of the above problems,efforts have been made to develop technologies that can assist withproper placement of tools during surgery. For example, U.S. Pat. No.8,057,482 B2 describes a handheld surgical tool with certain navigationfeatures that are provided to improved positional accuracy. The toolfeatures a button which must be pressed when the device achieves itsbasic reference position, which zeros the tool. Once this isaccomplished, the tool can be freely manipulated by the surgeon, and itwill show its positioning in space on three numerical displays providedat its casing. The displays show three-dimensional angular orientationof the tool in space. This device generally improves a surgeon's abilityto determine positioning of the tool in an area with limited access, andconsequently restricted visual observance. However, it can be ratherdifficult for the surgeon to control the plurality of displays in orderto check whether a desired orientation has already been reached or ismaintained. Moreover, the device is not configured to compare thelocation of the surgical tool to a desired orientation, nor is itconfigured to generate model(s) of the anatomy such that the surgeon canvisualize placement of the surgical tool. Thus, the surgical toolaccording to U.S. Pat. No. 8,057,482 B2 does not adequately preventmisalignment of the surgical tool during a medical procedure.

Patient-specific instrumentation (PSI) has become popular in orthopedicsubspecialties such as total hip, knee, and shoulder arthroplasty,pelvic and acetabular procedures, and spinal deformities, with varyingdegrees of success. However, PSI has the disadvantages of requiring alead time of two or more weeks to receive the instrument before surgery,and during surgery it is not possible to modify the implant that wasselected or its orientation.

Thus, there remains a need in the art for orthopedic implantationprocedures that are reliable and reproducible, and that results inaccurate positioning and alignment of the implant.

SUMMARY

Some of the main aspects of the present invention are summarized below.Additional aspects are described in the Detailed Description of theInvention, Example, and Claims sections of this disclosure. Thedescription in each section of this disclosure is intended to be read inconjunction with the other sections. Furthermore, the variousembodiments described in each section of this disclosure can be combinedin various ways, and all such combinations are intended to fall withinthe scope of the present invention.

Accordingly, the disclosure provides a surgical navigation system foruse in a patient, comprising (a) a handheld surgical tool withcomputer-aided navigation, wherein the handheld surgical tool comprisesa handle and an instrument shaft; and (b) a graphical user interface(GUI) module, wherein the GUI module comprises at least one computingdevice and a visual display that is configured to indicate the locationof the handheld surgical tool. In some embodiments, the surgicalnavigation system also comprises an imaging device.

The handle may comprise a processor and at least one sensor unit. The atleast one sensor unit may comprise 3-axis accelerometer, a 3-axis rategyroscope, a 3-axis magnetometer, or a combination thereof. In someembodiments, the at least one sensor unit is configured to generateorientational data of the handheld surgical tool.

The processor or the at least one computing device may be configured todetermine the orientation of the handheld surgical tool based on theorientational data. In some embodiments, the processor or the at leastone computing device is configured to compare the orientation ofhandheld surgical tool with at least one preset target orientation.

The visual display may be configured to indicate any deviation of theorientation of the handheld surgical tool from the at least one presettarget orientation.

The imaging device may be configured to generate data that can betransformed into the three-dimensional image or contour. The imagingdevice may comprise a time-of-flight camera, a pair of stereoscopiccameras, or a three-dimensional scanning tool.

In some embodiments, the surgical navigation system may further compriseat least one marker that is attachable to a portion of the patient'sanatomy, and in certain embodiments two markers that are each attachableto a different portion of the patient's anatomy. A marker engager can beattached to the handheld surgical tool, in which the marker engager isconfigured to engage with the one or more markers at a set orientation.The processor may be configured to detect an orientation of the one ormore markers and, in some embodiments, configured to measure angularorientations and linear distances of anatomical features in relation tothe one or more markers.

In some embodiments, the computing device is configured to generate athree-dimensional model or contour of a surface of the patient's anatomyor portion thereof The three-dimensional model or contour may begenerated based upon data from the imaging device.

In some embodiments, the GUI module is configured to receive data on oneor more of location of the handheld surgical tool, deviation of thelocation of the handheld surgical tools from a desired location, imagesof the patient's anatomy or portion thereof, and a three-dimensionalmodel of the patient's anatomy or portion thereof. In certainembodiments, the GUI module is configured to overlay one or more of:images of the patient's anatomy or portion thereof, thethree-dimensional model of the patient's anatomy or portion thereof, thelocation of the handheld surgical tool, the desired location for thehandheld surgical tool. In further embodiments, the GUI module isconfigured to display one or more of images of the patient's anatomy orportion thereof, the three-dimensional model of the patient's anatomy orportion thereof, the location of the handheld surgical tool, the desiredlocation for the handheld surgical tool. In some embodiments, the GUImodule is configured to display the overlay.

In embodiments of the invention, the GUI module is configured toqualitatively or quantitatively indicate the deviation between thelocation of the handheld surgical tool and the desired location of thehandheld surgical device. The deviation may be indicated by one or morevisual, aural, tactile or indications.

The surgical navigation system may be used in a method of implanting aprosthesis in a patient undergoing a joint arthroplasty. Further, thesurgical navigation system may be used to improve the accuracy ofprosthesis implantation in patient undergoing a joint arthroplasty. Thejoint arthroplasty may be hip arthroplasty, knee arthroplasty, orshoulder arthroplasty.

Accordingly, another aspect of the invention is directed to a method ofimplanting a prosthesis in a patient undergoing a joint arthroplastyusing the surgical navigation system of the invention. The method maycomprise (i) exposing the joint of the joint arthroplasty; (ii) placingone or more markers on anatomical features of the joint; (iii) engagingthe handheld surgical tool with the one or more markers and recordingorientation of the handheld surgical tool during the engagement; (iv)registering the orientation of the handheld surgical tool relative tothe orientation of the joint; (v) displaying the orientation of thehandheld surgical tool and a predetermined target orientation for thehandheld surgical tool, on the visual display; and (vi) implanting theprosthesis using the handheld surgical tool and the visual display,wherein the orientation of the handheld surgical tool is adjustedaccording to the predetermined target orientation for the handheldsurgical tool.

Alternatively, the method may comprise (i) exposing the joint of thejoint arthroplasty; (ii) recording an image data of the anatomy of thejoint, or a portion thereof, using the imaging device; (iii) generatinga three-dimensional image or contour of the anatomy of the joint, or theportion thereof, using the GUI module; (iv) engaging the handheldsurgical tool with the one or more anatomic features on the joint andrecording orientation of the handheld surgical tool during theengagement; (v) registering the orientation of the handheld surgicaltool relative to the orientation of the joint; (vi) displaying one ormore of the three-dimension image or contour, the orientation of thehandheld surgical tool, and a predetermined target orientation for thehandheld surgical tool, on the visual display; and (vii) implanting theprosthesis using the handheld surgical tool and the visual display,wherein the orientation of the handheld surgical tool is adjustedaccording to the predetermined target orientation for the handheldsurgical tool.

BRIEF DESCRIPTION OF THE DRAWINGS

The following description, given by way of example and not intended tolimit the invention to the disclosed details, is made in conjunctionwith the accompanying drawings, in which like references denote like orsimilar elements and parts, and in which:

FIG. 1 illustrates a perspective view of a handheld surgical toolaccording to embodiments of the invention.

FIG. 2 illustrates function blocks of elements of a surgical navigationsystem according to embodiments of the invention.

FIG. 3 illustrates components of a surgical navigation system accordingto embodiments of the invention.

FIG. 4 illustrates an example of range of motion model inputs shown on avisual display according to embodiments of the invention.

FIG. 5 illustrates components of a surgical navigation system in whichan imaging device 500 is integrated with, or otherwise attached to, thehandheld surgical tool, according to embodiments of the invention.

FIGS. 6A and 6B illustrate the supine (FIG. 6A) and lateral decubitus(FIG. 6B) positions, in which the patient may lie during a hiparthroplasty.

FIG. 7 illustrates a Cross-anterior superior iliac spine (ASIS) baraccording to embodiments of the invention.

FIGS. 8A and 8B illustrate use of the Cross-ASIS bar according toembodiments of the invention. FIG. 8A shows the placement of theCross-ASIS bar on the ipsilateral ASIS and the contralateral ASIS, andFIG. 8B shows the location of the ipsilateral ASIS and the contralateralASIS on the pelvis.

FIGS. 9A and 9B illustrate use of the Cross-ASIS bar according toembodiments of the invention. FIG. 9A shows the placement of theCross-ASIS bar on the ipsilateral ASIS and the pubis symphysis, and FIG.9B shows the location of the ipsilateral ASIS and the pubis symphysis onthe pelvis.

FIGS. 10A and 10B illustrate use of the handheld surgical device toregister the front plane according to embodiments of the invention.

FIGS. 11A and 11B illustrate use of the handheld surgical device toregister the horizontal plane according to embodiments of the invention.

FIGS. 12A and 12B illustrate components of a surgical navigation systemduring an operating step, according to embodiments of the invention. Inparticular, FIG. 12A illustrates placement of a first marker on thepelvis, and FIG. 12B illustrates engagement of the handheld surgicaltool with the marker.

FIGS. 13A and 13B further illustrate components of a surgical navigationsystem during an operating step, according to embodiments of theinvention. In particular, FIG. 13A illustrates placement of a secondmarker on the femur, and FIG. 13B illustrates repositioning of the legto a neutral position.

FIGS. 14A and 14B further illustrate components of a surgical navigationsystem during an operating step, according to embodiments of theinvention. In particular, FIG. 14A illustrates engagement of thehandheld surgical tool with the second marker placed on the femur; andFIG. 14B illustrates using the handheld surgical tool to capture thefemoral axis that is in line with the distal aspect of the femur.

FIG. 15 illustrates the linear measurement device (LMD) according toembodiments of the invention.

FIG. 16 illustrates components of a surgical navigation system during afurther operating step according to embodiments of the invention, inwhich an imaging device images the relevant patient anatomy.

FIG. 17 illustrates an example of an initial leg offset scan withmarkers detected shown on a visual display according to embodiments ofthe invention.

FIG. 18 illustrates components of a surgical navigation system during afurther operating step according to embodiments of the invention, inwhich the imaging device images the relevant anatomy after resection anda plurality of points on the acetabulum are located.

FIGS. 19A-19C illustrate component of a surgical navigation systemduring a further operating step according to embodiments of theinvention. FIG. 19A shows engaging the handheld surgical tool with thefirst marker in order to establish a reference point; FIG. 19B shows useof a cup impactor attached to the handheld surgical tool; and

FIG. 19C shows how the visual display provides guidance to properlyorient the cup impactor.

FIG. 20 illustrates an example of brush selection of points on thelunate surface of the acetabulum for center of rotation detection shownon a visual display according to embodiments of the invention.

FIG. 21 illustrates an example of detected center of rotation andacetabular diameter shown on a visual display according to embodimentsof the invention.

FIG. 22 illustrates an example of a targeting interface for reaming andcup orientation navigation shown on a visual display according toembodiments of the invention.

FIG. 23 illustrates selection of cup orientation angles from range ofmotion model output graph shown on a visual display according toembodiments of the invention.

FIG. 24 illustrates components of a surgical navigation system during afurther operating step according to embodiments of the invention, inwhich a new three-dimensional contour/surface is generated fromadditional scanning.

FIG. 25 illustrates trial center of rotation scan, displaying detectedmarker, detected trial head and center of rotation, selected points onthe rim of the implanted cup, and detected cup orientation, and shown ona visual display according to embodiments of the invention.

FIG. 26 illustrates a demonstration of the K-Wire being drilled into theglenoid while being guided by the handheld surgical tool and attachedK-Wire guide.

FIGS. 27A and 27B illustrate an example of the K-Wire trajectoryguidance interface provided by the surgical navigation system accordingto embodiments of the invention.

DETAILED DESCRIPTION OF THE INVENTION

Detailed embodiments of the present surgical navigation system, andcorresponding methods, are disclosed herein. However, it is to beunderstood that the disclosed embodiments are merely illustrative of asurgical navigation system, and of methods, that may be embodied invarious forms. In addition, each of the examples given in connectionwith the various embodiments of the systems and methods are intended tobe illustrative, and not restrictive. Further, the drawings andphotographs are not necessarily to scale, and some features may beexaggerated to show details of particular components. In addition, anymeasurements, specifications, and the like shown in the figures areintended to be illustrative, and not restrictive. Therefore, specificstructural and functional details disclosed herein are not to beinterpreted as limiting, but merely as a representative basis forteaching one skilled in the art to variously employ the present systemand methods.

Surgical Navigation System

The surgical navigation system of the present invention comprises ahandheld surgical tool and a graphical user interface (GUI) module, and,optionally, an imaging device. As shown in FIG. 1, the handheld surgicaltool 200 may comprise a handle 210 and an instrument shaft or end tool250. The GUI module 400 may comprise a computing device 405 and at leastone visual display 410, and optionally at least one memory unit forstoring data (see FIG. 2).

The instrument shaft 250 attaches to the proximal end of handle 210. Theproximal end of handle 210 is configured to accommodate multipledifferent types of instrument shafts, for example, using a universal orcommon connection. The instrument shaft 250 includes a distal end tip251 and a proximal end 252.

In some embodiments, the instrument shaft 250 may itself be a tool. Inother embodiments, the instrument shaft 250 may be configured as anattachment point to receive a tool in an interchangeable fashion, suchas a reamer, cutting jig, cup impactor, marker engager, an X-jig (asdescribed herein), etc.

In certain embodiments, the instrument shaft 250 may be a guide havingan internal hollow conduit for guiding a surgical instrument, and inorder to place the surgical instrument in a correct manner, the surgicalinstrument may be placed with its tip on the target location in acertain orientation, which determines the angle with which the surgicalinstrument will interact with the target location.

The handle may comprise multiple components enclosed in a housing. Forexample, the handle may comprise a processor 220 and at least one sensorunit 260, (also known as an inertial measurement unit) as shown in FIG.2. Optionally, the sensor unit may be a separate component, for example,in a sensor housing that can be attached to the handle.

The sensor unit 260 can provide orientational data of the handheldsurgical tool. According to certain embodiments, the sensor unit 260 maycomprise an inertial sensor in the form of a 3-axis accelerometer, a3-axis rate gyroscope, a 3-axis magnetometer, or a combination thereof.In some embodiments, the sensor unit 260 may comprise a 3-axisaccelerometer and 3-axis gyroscope. In certain embodiments, the sensorunit 260 may also comprise a temperature sensor. The processor 220 orthe computing device 410 may be configured to determine the orientationof the handheld surgical tool 200 in space based on the orientationaldata from the sensor unit(s).

According to alternative embodiments, the sensor unit 260 may compriseother types of sensors configured to produce positional information. Adata fusion module (not shown) may be configured to process the outputsignals of the sensor unit in a generally known manner (filtering,normalizing, calibrating, etc.) and, in some embodiments, to merge theprocessed signals in order to produce a unified consolidated positionoutput signal. For this merging, generally known techniques may be used(for example, Kalman-filter, Quaternion-gradient, complementary filter,etc.). Optionally, the data fusion module is further configured to codethe output by Quaternions in order to avoid singularities, such asgimbal lock issues. According to an alternative embodiment, the datafusion module may be incorporated into processor 220.

The consolidated output position signal of the data fusion module issupplied to processor 220. Based on this signal a conversion to Eulerangles or three-dimensional vectors may be performed. In someembodiments, the output position signal includes data based onquaternions, which is subsequently converted to three-dimensionalvectors and from there to 2D vectors. The position memory 224 isconfigured to store all positional data.

A set key 240 may be provided on the handle 210 of the handheld surgicaltool 200 and used to calibrate the tool or store a current position ofthe tool. As an alternative to the set key 240, a microphone 240′ may beprovided, in which voice activation could be substituted for physicallypressing the set key 240.

In embodiments of the invention, the processor 220 may be operativelyconnected to the position memory 224, the set key 240, and left controlkey 242 and right control key 244. The control keys may alter certaintrajectories as well as provide a means for a user to interact with theGUI module 400 directly. Further, processor 220 may be configured torecall data from position memory 224.

According to certain embodiments, the processor 220 is configured fortwo operation modes, which may be selected by activation of the set key240. In a first operation mode, the processor 220 is configured torecall stored incomplete position from position memory 224 generally,and to compare it against an actual position indication as supplied bythe sensor unit(s) 261. Based on the difference between these positionindications, the processor 220 generates a first deviation signal forone direction, such as inclination (or for another direction, such asanteversion). In the second operation mode, the processor 220 isconfigured to recall the full position indication and to compare itagainst the actual position indication as supplied by the sensor unit(s)261. Based on the difference between these position indications itgenerates a different deviation signal that has one more dimension thanthe first deviation signal, such as inclination and anteversion inpreferred embodiments. Switching from the first to the second operationmode may be controlled, in some embodiments, by the user by means of setkey 240. Although certain embodiments herein describe the deviationsignals being generated and supplied by processor 220, the invention isnot so limited. For example, processing of positional data may becarried out by the GUI module, the handheld surgical tool, orcombinations thereof

The deviation signals are supplied to, or in some embodiments generatedby, the GUI module 400 of the surgical navigation system. The GUI module400 may comprise a computing device 405 and at least one visual display410, and optionally at least one memory unit for storing data (forexample, positional data from the handheld surgical tool 200). In someembodiments, the GUI module 400 may be configured to indicate directionand position—and in a qualitative and/or quantitative manner,magnitude—of any deviation as defined by the deviation signals. The GUImodule 400 may also include a visual indicator, the visual indicatorbeing formed by a visual display 410. The visual display 410 forming thevisual indicator, according to embodiments, comprises a bullseye displaywithin a crosshair pattern (see FIG. 3). According to some embodiments,and as shown in FIG. 2, the GUI module 400 may be in communication withthe handheld surgical tool 200. For example, the GUI module 400 maycommunicate wirelessly with handheld surgical tool 200 via wirelesstransmitters 248, 249.

According to some embodiments, the handheld surgical tool 200 mayinclude a tactile indicator 246, an aural indicator 247, a visualindictor (not shown), or combinations thereof The tactile indicator 246may comprise two pairs of vibration transducers 246′ and 246″ arrangedon opposite lateral sides of the housing 210 and on the top and bottomside of the housing 210, respectively. As an aural indicator, aloudspeaker 247 may be provided, which is driven by a sound module 247′forming a part of either the handheld surgical tool 200 or the GUImodule 400. The visual indictor may be in the form of a display, such asan LCD display, or can take the form of one or more lighting devices,such as LEDs.

Further, the handheld surgical tool 200 may be configured with awireless transmitter 248 that is configured for communication with awireless transmitter 249 on the GUI module 400. According to certainembodiments, the tactile indicator 246, aural indicator 247, and/orvisual indictor may replace visual display 410. In such embodiments, thebullseye display within a crosshair pattern may be omitted, and rather,the handheld surgical tool 200 may provide the indication of directionand position, such as via audio cues provided by aural indicator 247.

A rechargeable or disposable battery 270 may be provided that suppliesthe various components of the handheld surgical tool via supply lines(not shown). In order to recharge the battery 270, a recharging coil 271may be provided which is configured for wireless charging.

The imaging device 500 of the surgical navigation system is configuredto image portions of the anatomy in order to generate imaging data thatis used to create three-dimensional surface(s)/contour(s), as shown inFIG. 3. According to certain embodiments, the imaging device 500 isintegrated or otherwise attached to the handheld surgical tool 200.According to alternative embodiments, the imaging device 500 is aseparate device and is configured to communicate with handheld surgicaltool 200 and/or GUI module 400.

In some embodiments, the surgical navigation system may comprise aprocessor, having instructions stored on a non-transitory computerreadable medium, that when executed by the processor, cause theprocessor to operate in two distinct operating modes, wherein in one ofthe two distinct operating modes a reduced position indication isprocessed. The reduced position indication is a position indicationwhich lacks at least one indication for one degree of freedom comparedto the full position indication of the second operating mode. Forexample, in Euclidean space three angle indications can be used todescribe an orientation of a device in a three-dimensional space. But ifthe absolute location does not need to be monitored, then two, insteadof three, of the angles may be monitored, which will not provide a fullyfixed orientation, but will instead retain one degree of freedom. If,for example, angles for roll, pitch and yaw are used, then an incompleteposition indication could only have indications of roll and yaw, leavingpitch as a degree of freedom. As another example, if only two ratherthan three angles are to be used (e.g., if roll is to be ignored), afull position indication will have both angles (e.g., pitch and yaw),whereas an incomplete position indication would indicate only one angle(e.g., yaw only). Detailed embodiments implementing the two operatingmodes, which are incorporated herein, are further described inco-pending U.S. patent application Ser. No. 16/442,155. Additionally,and with specific reference to hip arthroplasty applications, the anglesmay be the cup inclination and anteversion.

Methods of Using the Surgical Navigation System

The surgical navigation system of the present invention may be used inmethods of implanting a prosthesis in a patient undergoing a jointarthroplasty, and methods of improving the accuracy of prosthesisimplantation in a patient undergoing a joint arthroplasty.

For such methods, the surgical navigation system can be set up withinthe operating room. In order to do so, and as illustrated by FIG. 3,imaging device 500 may be located next to the patient that is on anoperating table.

In embodiments in which the sensor unit 260 is to be attached to thehandle 210, the handheld surgical tool 200 may be assembled. Accordingto these embodiments, the handle 210 of handheld surgical tool 200 issterile packed. The sterile pouch is opened, a lid is removed from theback of the handle 210, and the sensor unit 260 is inserted until fullyengaged and flush with the handle 210. The lid may then be closed,sealing the sensor unit 260 within the handle 210.

A desired instrument shaft 250 (i.e., end tool) is chosen and attachedto the proximal end of handle 210.

The handheld surgical tool 200 may be activated. By way of example only,removal of a pull tab on handheld surgical tool 200 will enable battery270 to power on the components handheld surgical tool 200.Alternatively, a switch may be pressed to power on components handheldsurgical tool 200.

In some embodiments, the handheld surgical tool 200 may undergoinitialization. During initialization, the handheld surgical tool 200measures the direction of gravity using its sensor unit 260, such thatthe position in space of the handheld surgical tool 200 is establishedagainst a coordinate system. In some embodiments, the handheld surgicaltool 200 must remain motionless during initialization. An indicator mayshow that initialization is complete. An example of an indicatorincludes, but is not limited to, a light-emitting diode (LED) light,such as a green LED light.

The term “position in space” and its short form “position” in context ofthe present invention generally refers to a system with six degrees offreedom that may comprise absolute location and orientation. Thelocation might be represented as coordinates of a three-dimensionalspace with perpendicular axes (e.g. X, Y, Z), while the orientationmight be provided by Euler angles (e.g., yaw, pitch, and roll; alpha α,beta β; and gamma γ; phi φ, theta θ, and psi ψ) or by quaternions. Inpreferred embodiments, the coordinate system of the handheld device willbe established relative to gravity, such that the y-axis is orientedopposite to the direction of gravity.

By means of definition, a coordinate system for the human body may bedefined featuring an X-axis as side to side (left to right, right toleft, i.e., lateral-medial direction), a Y-axis as up and down (feet tohead, head to feet, i.e., superior/cranial-inferior/caudal direction),and a Z-axis (front to back, back to front, i.e.,anterior/ventral-posterior/dorsal direction) orthogonal to the X- andY-axis indicating depth. Alternatively, the coordinate system for thehuman body may be such that the Y-axis is opposite the direction ofgravity; as a result, the alignment of the coordinate system compared tothe human body will depend on the position of the patient. For example,if the patient is lying down on his/her back with the head towards theright, the Y-axis will align with the anterior/ventral-posterior/dorsaldirection, the X-axis will align with thesuperior/cranial-inferior/caudal direction, and the Z-axis will alignwith the lateral-medial direction.

The imaging device 500 may image the relevant anatomy of the patient.The connection (for example, wireless) between the handheld surgicaltool 200 and the GUI module 400 may be activated (for instance, bykeying in a code indicated on the handheld surgical tool 200), and theconnectivity may be verified (for example, by moving a part of thehandheld surgical tool 200) by confirming that a corresponding icon (forexample, a handle icon) on visual display 410 moves at the same time.

Aspects of the procedure (for example, surgical level, implant side, cupsize, etc.) may be pre-stored or provided to the GUI module 400 and/orhandheld surgical tool 200. For instance, based on provided aspects ofthe desired surgical procedure, default values for starting targetangles appropriate for the intended surgery can be inputted. The GUImodule 400 and/or handheld surgical tool 200 is programmed with thesedefault target angle values and/or distance values for arthroplastycomponent positioning (for example, from research, published sources, orpreoperative imaging data), for each type of surgery, that approximatethe angles with which the surgical tool will need to be oriented for aneffective surgery. This eliminates or minimizes the amount of adjustment(in other steps, described below) needed to establish a trajectory forthe actual surgery—such as by allowing the initial trajectory to bewithin a crosshair on the visual display 410 of the GUI module 400.

By way of an example, for a hip arthroplasty, a “Range of Motion model”may be chosen as the cup replacement model, and the visual display 410of the GUI module 400 may appear as shown in FIG. 4, which indicatesthat the desired post-operative range of motion of the patient, thegeometric parameters of the implant, and the patient's pelvic tilt arerequired as inputs. The Range of Motion model is configured to generatea “heatmap” of cup orientations defined by anteversion and inclinationangles based on the inputs. The heatmap will show, for example by usinga green color, where the orientations will result in impingement-freemotion.

According to embodiments, and as exemplified in FIG. 3 , one or moremarkers may be placed on a portion of the patient's anatomycorresponding to the location of the surgical procedure, i.e., on one ormore of the bones involved in the joint arthroplasty. The markers may bedesigned to engage with the handheld surgical tool 200. In preferredembodiments, a tool such as a marker engager 610 may be attached to thehandheld surgical tool 200, for example at the distal end tip 251 of thehandheld surgical tool 200.

In some embodiments, a first marker 601, such as a bone screw, is placedon a bone forming part of the joint. In some embodiments, the firstmarker 601 may have a unique shape and the marker engager 610 attachedto the handheld surgical tool 200 may have a complementary shape, suchthat the first marker 601 and the marker engager 610 can mate in asingle orientation. This allows for the marker engager 610 to fit with,over (or within) the first marker 601 in a specific orientation. Onceplaced, the marker engager 610 is mated to the first marker 601, andthen the handheld surgical tool 200 is zeroed/calibrated to thisposition (for example, by pressing set key 240, or by a surgical teammember or representative clicking a button on GUI module 400). Thelocation of the first marker 601 may be previously established by thesystem (for example, via detection in a three-dimensional surface/model700) of the anatomy, and as such the location of the handheld surgicaltool 200 is similarly known. In this way, zeroing of the location ofhandheld surgical tool 200 within the navigation field can beeffectuated. This also allows for the generation of positionalinformation of the first marker 601 and the handheld surgical tool 200relative to it.

The marker engager 610 may then be removed from the first marker 601 andbrought in contact with one or more other features of the anatomy so asto capture a horizontal vector. The location of the handheld surgicaltool 200 at this position is then stored, for example, by depression ofset key 240. With this positional information, the relative position ofthe first marker 601 to the horizontal vector 301 is determined.

In some embodiments, a second marker 602 (similar to or the same as thefirst marker 601) can be placed on another portion of the patient'sanatomy, depending upon the surgical procedure, such as on another bonethat forms part of the joint. Once both the first marker 601 and thesecond marker 602 are placed the patient is repositioned such that aneutral position is achieved.

In some embodiments, similar to the first marker 601, the marker engager610 attached to the handheld surgical tool 200 is mated to the secondmarker 602, and then the handheld surgical tool 200 is zeroed/calibratedto this position. The location of the second marker 602 may bepreviously established by the system (e.g., via detection in athree-dimensional surface/model 700) of the anatomy. The marker engager610 may then be removed from the second marker 602 and brought incontact with one or more other features of the anatomy so as to capturea horizontal vector. The location of the handheld surgical tool 200 atthis position is then stored.

In some embodiments, the imaging device 500 may image the relevantpatient anatomy, including the first marker 601 and, if present, thesecond marker 602. In some embodiments, the imaging device 500 may be athree-dimensional scanning tool, which captures data corresponding tothe shape/surface of the bone on which the marker(s) are located, aswell as the location and orientation of the marker(s). Such data may becaptured by moving the scanning tool around the relevant areas of thebone and capturing imaging data during the movement.

A processor (for instance, the processor of the handheld surgical tool,the processor of the GUI module, etc.) may obtain the imaging data andgenerate a three-dimensional surface/model of the anatomy and themarker(s). It is to be noted that three-dimensional surface/model onlyneeds to be a representation of the relevant portion of the anatomybeing scanned and does not need to be a representation of the entireanatomical structure. The processor, having instructions stored on anon-transitory computer readable medium, that when executed by theprocessor, cause the processor to detect relevant features of theanatomy from the three-dimensional surface/model with the aid of themarker(s). The processor may also calculate relevant orientations (forexample, angular orientations) and distances with regards to thepatient's anatomy. Such information may help add precision indetermining how the bone should be modified for surgery (for example,where the bone should be cut, shaved, etc.).

In some embodiments, the process of attaching markers and scanningdescribed herein may be repeated as necessary. For example, in someembodiments additional markers may be attached to different bones oranatomical features.

In alternative embodiments of the invention, markers are not attached tothe bone or other anatomical features and, instead, the handheldsurgical tool 200 is placed next to the target anatomy of the patient.The imaging device then images the target anatomy (for example, the hip)along with the handheld surgical tool 200. From this imaging data thelocation of the handheld surgical tool 200 is detected by the processor.The handheld surgical tool 200 can be calibrated to the navigation spacebased upon this information.

In some embodiments, the surgery may require cutting or removing aportion of bone. Using positional information that has been captured,the visual display 410 can indicate where, for example, a cutting jig isto be placed such that it properly aligns with particular anatomicfeatures so that the location and angle of the cut is accurate.

In certain embodiments, the distal end 251 of the instrument shaft 250of the handheld surgical tool 200 can be placed in real space at thestarting point, such as within or on a marker in order to establish astarting reference point for the procedure. In preferred embodiments,the starting point may be registered on GUI module as a point in thevirtual space of the system (for example, preferably, X=0, Y=0, Z=0;that is, the starting point is preferably set as the origin point in thevirtual space of the system). Also, a proximal end 252 of the instrumentshaft 250 may be registered as a point in the virtual space of thesystem relative to the starting point in the virtual space of thesystem, so that the orientation of the instrument shaft 250 in realspace relative to the starting point in real space, and relative to thedefault target angle/trajectory/orientation, is determinable andrepresentable by the system in the virtual space of the system. Thehandheld surgical tool 200 can be moved in real space to angulate theinstrument shaft 250 about the starting point in real space until thevisual display 410 indicates that the orientation of the shaft in realspace relative to the starting point is aligned with the default targetangle/trajectory/orientation.

For example, a predefined trajectory may be recalled from an associatedmemory (for instance, positional memory 224) and the handheld surgicaltool 200 can be moved in real space and a position of an indicator onvisual display 410 (for example, a green dot representing the proximalend 252 of the instrument shaft) is shown relative to a position of atarget point (for example, the distal end tip 251 corresponding to thecenter of a bullseye's cross-hairs), and when the positions are aligned,the system has determined that the instrument shaft 250 is oriented inreal space, relative to the predefined trajectory (for example, anestablished trajectory based on the literature or preoperative imagingdata), and the display 410 alerts the user to the alignment (forexample, by changing the GUI module color to predominantly green).According to certain embodiments, the predefined trajectory is basedupon pre-planned inclination/anteversion, etc., as determined by thesurgeon. According to alternative embodiments, patient images may beused as an input to validate the predefined trajectory. If thepredefined trajectory is satisfactory, the surgical procedure is theneffectuated (for instance, reaming or cutting of the bone).

In addition, a three-dimensional surface/contour 700 can be generatedand displayed on visual display 410 showing the relevant anatomy, theinstrument shaft 250 of the handheld surgical device 200, and thehandheld surgical device 200. The visual display 410 may also indicate,on the image or three-dimensional surface/model, the angle of theorientation of the shaft (for example, by a line along the longitudinalaxis of the shaft). Additionally, visual display 410 presents a relativeangle/trajectory/orientation indicator changeable in virtual space (forexample, a line rotatable in virtual space within the three-dimensionalsurface/model about the starting point 256, corresponding to thelocation of distal end tip 251). The user can change theangle/trajectory/orientation of the indicator in virtual space from thedefault angle/trajectory/orientation (foe instance, referencing anatomiclandmarks shown on the image or in the three-dimensional surface/model)using the control keys 242 and 244, directly on GUI module 400, or byother suitable means. For example, if the user sees that indicator isnot properly oriented in relation to the acetabulum, the user can changethe angle/trajectory/orientation of the indicator until the line passesthrough the desired anatomy.

In preferred embodiments, the user can confirm the desiredangle/trajectory/orientation, for example, by pressing set key 240. Forinstance, when the user determines that is at the appropriateangle/trajectory/orientation, the user can press set key 240. Uponconfirmation, the target angle/trajectory/orientation is changed fromthe default angle/trajectory/orientation (for example, that was takenfrom research and literature sources) to the desiredangle/trajectory/orientation (for example, that has been established bythe user). Data for the new target angle/trajectory/orientation (i.e.,for the desired angle/trajectory/orientation) is then saved intoposition memory 224. The data for the new targetangle/trajectory/orientation may additionally or alternatively be storedin position memory housed externally to the housing of the handheldsurgical tool 200—for example, in a separate device like a separatecomputer, hard drive, etc. This then locks in the desiredangle/trajectory/orientation.

The handheld surgical tool 200 can be angulated and the visual display410 can provide an indication of the location of handheld surgical tool200, and indicate when the tool is aligned with the new, desiredangle/trajectory/orientation. Preferably, when the positions arealigned, the handheld surgical tool 200 is maintained in real space inthe aligned position, and the site is prepared (for instance, thesurgeon reams the acetabulum, places an acetabular cup, etc.). At anytime during the procedure, imaging can be used to check the accuracy ofthe chosen three-dimensional trajectory/orientation/position.

According to further embodiments, initial defaultangle/trajectory/orientation values may be based upon direct targeting.The initial three-dimensional trajectory/orientation/position can bedetermined by attaching hardware (for instance, fixation pins) to thetarget anatomy and then determining the trajectory/orientation at whichthe hardware is attached. For example, the system can capture thedigital trajectory/orientation of a manually placed instrument orimplant. According to traditional surgical methods when targeting forimplant delivery, it is not uncommon to provisionally place a trialimplant, guidewire, temporary fixation pin, drill bit, or the like, andtake a radiograph to assess the positioning of the provisional placementin relation to known landmarks. In a fully manual environment, thesurgeon would need to make an analog adjustment, such as, for example,the final implant placement should be oriented a few degrees morelateral and a few degrees upward. This process is arbitrary, errorladen, requires a high level of spatial orientation awareness, and canresult in misjudgments and improperly placed hardware. The surgicalnavigation system 100 can improve upon this process. The instrumentshaft 250 of the handheld surgical 200 can be placed over aprovisionally directed trial, guidewire, fixation pin, or the like, andthe system can capture the digital orientation in real time, allowingthe surgeon to more accurately adjust the final placement. According toan illustrative example, a temporary element (for instance, trialacetabular cup) is implemented. Instrument shaft 250 is then attached(or placed against) this fixation element. Once aligned, thethree-dimensional trajectory/orientation of shaft 250 can be registered(for instance, by pressing the set key 240). Thereafter the shaft can beremoved. Imaging device 500 then acquires first imaging data (forinstance, allows for the creation of a first three-dimensionalsurface/model), which depicts the patients anatomy and the fixationelement (or alternatively, X-rays of the relevant anatomy may be takento observe the fixation element). Similar to the process describedabove, the registered trajectory/orientation from the initial alignmentof the device provides an indication for this registeredtrajectory/orientation. Using control keys 242 and 244 (or the GUImodule), a target trajectory/orientation can be modified, until adesired trajectory/orientation is obtained, which can then be locked-in(for instance, by using the set key 240). Finally, the shaft 250 of tool200 is placed at the surgical site, and visual display 410 may display abullseye type display (as exemplified in FIG. 3 to guide properalignment of instrument shaft 250.

Once the bone is cut/reamed or otherwise modified according to theprocedure, a new three-dimensional contour/surface 700 may be generated,which is based upon image data generated by imaging the bone includingany markers. Updated calculations determining angles and positioning of,for instance, implant devices, can help identify where any adjustment tothe implant devices are needed.

According to further embodiments, imaging device 500 may be integratedwith, or otherwise attached to the handheld surgical tool 200, asillustrated by FIG. 5. In these further embodiments handheld surgicaltool 200 may include sensor units 261, and communicate with GUI module400. According to a variation thereof sensor units 261 as well asmarkers may be omitted. For example, with an integrated imaging device,the relative orientation of the handheld surgical tool 200 is fixed inrelation to the imaging device 500. Thus, movements of the handheldsurgical tool 200 are experienced by the imaging device 500.Accordingly, positional sensors do not need to measure the relativemovement of the handheld surgical tool 200 and instead the imaging dataitself can be used to detect movement of the handheld surgical tool 200.It is noted that a marker 605 may be placed on the anatomy in order toaid in orienting the handheld surgical tool 200.

Imaging device 500 may also be configured to project an image into thepatient. For example, according to certain embodiments, imaging device500 project a line beam (such as via laser projection) onto a bone tovisually indicate a cut location. Such embodiments may include amotorized head which allows imaging device 500 to be rotated/moved.Additionally, or alternatively, such an image may be projected onto thethree-dimensional surface/contour 700.

Hip Arthroplasty

In embodiments of the invention, the surgical navigation system of thepresent invention may be used for performing a hip arthroplasty. Inparticular, the surgical navigation system of the present invention maybe used to achieve correct implant positioning.

In some embodiments, the hip arthroplasty may comprise a pre-planningstep, in which different aspects of registration and/or implantation maybe set. For example, settings for placement of the acetabular cup mayinclude selection of a cup placement model that will be used forimplanting the cup at a desired orientation; a reference plane that willbe used for determining the desired cup orientation; and whether toinclude a final cup orientation measurement.

The cup replacement model may be selected from a Range of Motion modelor an Extended Lewinnek model. The Range of Motion model involvesapplication of an algorithm to calculate an impingement-free zone of cuporientations based on a target range of motion set, the patient's pelvictilt, and the 3D angular neck and stem orientation within the femur (HsuJ et al., J. Biomech., 82: 193-203, 2018). The Extended Lewinnek modeldefines the “Lewinnek Safe Zone” (Lewinnek GE et al, J. Bone Joint Surg.Am., 60-A: 217-220, 1978) as the target zone, but applies specific inputinformation.

The reference plane may be selected from the anterior pelvic plane orthe coronal plane. The anterior pelvic plane is an anatomic planedefined by the two anterior superior iliac spines (ASIS) and themidpoint of the pubic tubercles. The coronal plane is a functional planeand is defined as any vertical plane that divides the body into ventraland dorsal sections.

In some embodiments, the pre-planning step may also include selectingwhether to detect a change in leg length. If selected, different aspectsof the leg position can be measured before and after implantation,including leg length, mediolateral offset, and anteroposterior position,to determine what changes, if any, occurred. The selection may includerecording the initial orientation of the femur so that the femur can bereturned to the same orientation when performing the post-operativemeasurements.

To perform registration of the patient coordinate system, i.e., toestablish the relationship between the virtual frame of reference of thejoint (including orientation of the handheld surgical device 200) andthe actual frame of reference of the joint (e.g., the actual orientationof the joint), the handheld surgical tool may be used to capture vectorsthat correspond to an anatomical plane of the patient. Each vector iscaptured by recording the orientation of the handheld surgical tool(i.e., recording the current quaternion of the handheld surgical device)and the vector is constructed from the recorded quaternion. In preferredembodiments, at least two vectors, corresponding to two planes, arecaptured.

Different vectors may be captured depending on the position of thepatient, i.e., whether the patient is in a supine position (see FIG. 6A)or in a lateral decubitus position (see FIG. 6B). If the patient is in asupine position, the handheld surgical tool 200 can capture the sagittalplane and the anterior pelvic plane. In some embodiments, a tool, suchas a Cross-ASIS bar 900, may be used. As shown in FIG. 7, the Cross-ASISbar 900 comprises a bar 905 having a proximal end 907 and a distal end908, in which the proximal end 907 of the Cross-ASIS 900 is configuredto engage with the distal end tip 251 of the handheld surgical tool 200.The Cross-ASIS bar 900 further comprises a first foot 910 and a secondfoot 912 that extend in the same direction from the bar 905 and areperpendicular to the long axis of the bar 905. The Cross-ASIS bar 900 isattached to the handheld surgical tool 200, so that the orientation ofthe handheld surgical tool 200 can be recorded when the Cross-ASIS 900bar is identifying a plane. To register a sagittal plane, the first foot910 is placed on the ipsilateral ASIS 915 (i.e., ipsilateral to theoperative hip) and the second foot 912 is placed on the contralateralASIS 917, and the resulting quaternion of the handheld surgical deviceis recorded (see FIG. 8). From this quaternion, the vector can beconstructed.

In some embodiments, this vector pointing in the direction of the longaxis of the cross-ASIS bar may be projected onto the coronal plane ofthe patient. The coronal plane of the patient in supine position may beassumed to be the same as the plane perpendicular to the direction ofgravity, which is detected automatically when the handheld device ispowered on, and is used to define the Y-axis of the surgical handhelddevice 200; as a result, no correction for the Y-axis is needed. Thehandheld-device-to-patient adjustment quaternion may be defined as therotation between the unit X-axis and the inter-ASIS vector in handhelddevice coordinates projected onto the coronal plane. In someembodiments, these measurements are performed while the operating tableremains perpendicular to the direction of gravity (i.e., horizontal).

To register the anterior pelvic plane, two vectors are captured. Thefirst vector is the same vector as recorded for registering the sagittalplane, but after recording the first vector, the Cross-ASIS bar can bepivoted such that the first foot 910 remains on the ipsilateral theCross-ASIS bar and the second foot 910 is moved to the pubis symphysis920 of the ipsilateral pelvis (see FIG. 9). The vector is captured inthis pivoted position, and then both vectors can be used to identify andregister the anterior pelvic plane. This also registers the pelvic tilt.The pelvic tilt is the angle between the vector in patient coordinatesgiven by the long axis of the Cross-ASIS bar projected onto the sagittalplane and the positive Z-axis. When the pelvic tilt is not zero, theangles of inclination and anteversion subsequently reported are adjustedto the pelvic frame of reference.

If the patient is in a lateral decubitus position, the handheld surgicaltool 200 can be used to capture a frontal (coronal) plane and ahorizontal plane. As shown in FIG. 10, the front plane can be registeredby recording the vector created when the handheld surgical tool verticalacross the ASIS and it assumes that the patient is perfectly lateral andorthogonal to the floor. The horizontal plane can be registered byrecording the vector created when the handheld surgical tool is alignedwith the main axis of the patient (see FIG. 11).

In some embodiments, recordation of the handheld surgical device duringthis registration step generates a handheld surgical device-to-patientadjustment quaternion

In embodiments of the invention, one or more markers may be installed onthe pelvis and/or femur. The markers may be installed by a manual method(using a mallet or similar instrument to tap the end of the marker intothe bone and then screwing the marker until it is fully in the bone) ora power method (using a drill or the like to install the marker). Adrill can also be used to create a pilot hole before installing themarker by the manual method or before screwing in the marker.

In some embodiments, a first marker 601 can be attached to the pelvis800 as demonstrated in FIG. 12A. In preferred embodiments, the firstmarker 601 is attached on the superior-anterior rim of the acetabulum. Amarker engager attached to the handheld surgical tool 200 may be matedto the first marker 601 and then the orientation of the handheldsurgical tool 200 engaged with the first marker 601 may be recorded togenerate positional information of the first marker 601 relative to thehandheld surgical tool 200 (see FIG. 12B). In some embodiments, thispositional information may be referred to as the recorded markerengagement quaternion.

The recorded marker engagement quaternion and handheld surgicaldevice-to-patient adjustment quaternion can be used to construct twovectors in patient coordinates that define the pelvic markerorientation: one vector directed along the marker engagement axis andone vector perpendicular to define the roll. Mathematically, theengagement quaternion from the handheld device is adjusted to patientcoordinates by computing the Hamiltonian product:q_(engagement,patient)=q_(handtool to patient)* q_(engagement,handtool).Two orthogonal axes of the patient are rotated by this quaternion toobtain the marker engagement axis and roll vector.

A femoral resection is performed, which may include broaching the femurin-situ. According to some embodiments, after the femur 825 is properlyexposed, and as illustrated by FIGS. 13, 14, and 16, a second marker 602(for example, a bone screw) can be placed on the femur 825, and inparticular, on the greater trochanter (see FIG. 13A). A marker engager610 attached to the handheld surgical tool 200 can be engaged with thesecond marker 602 (see FIG. 14A). Second marker 602 may have a uniqueshape, while the marker engager 610 has a complementary shape, such thatthey can mate in a single orientation. This allows for the markerengager 610 to fit with, over, or within, second marker 602 in aspecific orientation. Once placed, the marker engager 610 is mated tosecond marker 602, and then the position of the handheld surgical tool200 is recorded (for example, by pressing set key 240, or by a surgicalteam member or representative clicking a button on GUI module 400).Because the location of the second marker 602 is previously establishedby the system (for example, via detection in the three-dimensionalsurface/model 700), the location of the handheld surgical tool 200 issimilarly known. The marker engager 610 may then be removed from thesecond marker 602 and, in some embodiments, the handheld surgical tool200 may be brought in contact with lateral aspect of the greatertrochanter, so as to capture femoral axis 302, which is a straight linein line with the distal aspect of the femur 825 (see FIG. 14B). Theposition of handheld surgical tool 200 may be stored, for example, bydepressing set key 240. With this positional information, the relativeposition of the second marker 602 to femoral axis 302 is determined, andthe relative angle of the horizontal axis 301 to femoral axis 302 isdetermined.

In some embodiments, once both first marker 601 and second marker 602are placed, the patient may be repositioned such that a neutral positionof the leg is achieved (i.e., neutral flexion/extension,adduction/abduction, and internal/external rotation) (see FIG. 13B).

In some embodiments, the handheld surgical tool may be used to measurethe initial leg position. In certain embodiments, a tool may be used forthe initial linear measurements, for example, a Linear MeasurementDevice (LMD) as shown in FIG. 15. The LMD 950 comprises a first arm 955having a proximal end 957 and a distal end 958, and a second arm 960having a proximal end 962 and a distal end 963. The first arm 955 andthe second arm 960 are connected by a joint 965 that allows the firstarm 955 and the second arm 960 to rotate relative to each other. Theproximal end 957 of the first arm 955 and the proximal end 962 of thesecond arm 960 are each configured to engage with a marker. The distalend 958 of the first arm 955 and the distal end 963 of the second arm960 are configured to engage with a marker engager 610 attached to thehandheld surgical tool 200. During use, the LMD 950 is engaged with boththe pelvic marker 60 land the femoral marker 602. The handheld surgicaltool 200 is engaged with the first arm 955of the LMD 950 and recorded,and the handheld surgical tool 200 is then engaged with the second arm960 of the LMD 900 and recorded. In the software, a vector representingeach of the arms 955, 960 of the LMD 900 is constructed in patientcoordinates from the recorded quaternion of the handheld surgical tool200. The second vector recorded is subtracted from the first vectorrecorded. This vector represents the distance between the two markers,pointing from the pelvic marker 601 to the femoral marker 602.

As illustrated in FIG. 16, imaging device 500 images the relevantpatient anatomy, including the first marker 601 and the second marker602. For example, the imaging device 500 may be a three-dimensionalscanning tool that captures data corresponding to the shape/surface ofthe pelvis and the location and orientation of the markers 601 and 602.A processor generates a three-dimensional surface/model 700 of thepelvis and the markers 601 and 602 from the imaging data. Bone features,such as the shape of the acetabulum (coronal and sagittal plane), aswell as the markers and their orientation in relation to patientanatomy, can be detected based upon three-dimensional surface/model 700.Additionally, the processor can calculate relevant orientations anddistances, such as intra-operative leg length (ILL), leg lengthdiscrepancy (LLD), and offset for the patient prior to (and after) thehip replacement procedure because the system has positional informationof marker 601 and 602, in a neutral position relative to one another andrelative to horizontal vector 301. This allows for the system todetermine a proper angle and a suitable starting location on the femur'sneck for cutting of the femur's head. Moreover, by imaging in theneutral position, an accurate leg length can be calculated.

In some embodiments, the three-dimensional scanning tool is used toobtain a single point cloud file in which both the pelvic and femoralmarkers are visible (see FIG. 17). The process may run a point cloudmatching algorithm on the three-dimensional scan to identify thelocation and orientation of each marker in scan coordinates. Pre-scannedpoint clouds of the individual markers with a known orientation may beprovided to the algorithm as source data for matching. The point cloudmatching algorithm can use random sample consensus to find anapproximate transformation (i.e., location and orientation) for thefirst marker 601 and second marker 602 in the target scan. Theapproximate transformation is then refined to an exact transformation byan iterative closest point calculation.

In embodiments in which the pelvic marker orientation has been recorded,the quaternion rotation between scan axes and patient axes can becalculated. First, the quaternion rotation q_(engagement correction)from the pelvic marker engagement axis in scan coordinates to theengagement axis in patient coordinates is calculated. Then, the roll isaccounted for by finding q_(roll correction) as the quaternion rotationfrom the roll vector in scan coordinates rotated byq_(engagement correction) to the roll vector in patient coordinates. Theoverall scan-to-patient coordinate quaternion is then:q_(scan to patient)=q_(roll correction)* q_(engagement correction). Thevector connecting the centers of the two markers is then calculated andrecorded in patient coordinates by rotating the same vector in scancoordinates by q_(scan to patient) as follows:v_(intermarker,patient)=q_(scan to patient)*V_(intermarker,scan)*q_(scan to patient) ⁻¹. The pelvic and femoral marker orientationvectors are similarly converted to patient coordinates.

In some embodiments, a rigid guide connecting both markers may be placedin the wound to simplify the process of obtaining a scan of bothmarkers. This guide may allow the three-dimensional scanner to follow afixed path from one marker to the other, thus avoiding the technicaldifficulty of scanning a path across mobile soft tissues.

In some embodiments, a mark 603 (e.g., divot, bur, or bowie) may befurther placed on the femoral head, as illustrated by FIG. 16. Theimaging unit images the surgical area again in order to capture markers601 and 602 and mark 603. As further illustrated by

FIG. 16, femoral axis 302 may be displayed on the subsequently generatedthree-dimensional surface/contour 700.

With this positional information the visual display 410 can indicatewhere a cutting jig is to be placed such that it properly aligns withfemoral axis 302 so that the femoral head is properly resected (i.e.,cut at the proper angle).

In some embodiments, imaging device 500 images the relevant anatomy,after resection, in order to generate relevant anatomical features, suchas features of the acetabulum. According to embodiments,three-dimensional surface/contour 700 is generated from the image dataand analyzed in order to locate a plurality of points 604 on theacetabulum, as illustrated by FIG. 18. These points, according to onepreferred embodiment, correspond to the acetabular notch and the top,left, and right acetabular rim. With this information the systemdetermines the coronal plane, which may be displayed on visual display410 in conjunction with the three-dimensional surface/contour 700.

A set of steps may be carried out to effectuate a computer aidedsurgical procedure. The handheld surgical tool 200 may be placed in realspace at the starting point, such as within/on marker 601 (e.g., via amarker engager 610), as illustrated by FIG. 19, in order to establish astarting reference point for the procedure.

In certain embodiments, the imaging device 500 obtains a single pointcloud file in which the pelvic marker and the lunate surface of theacetabulum are visible. A point cloud matching algorithm may be run onthe imaging data to identify the location and orientation of the pelvicmarker in scan coordinates, and the orientation is then adjusted topatient coordinates. In certain embodiments, in the UI, a brush selectortool 505 (see FIG. 20) may be used to select points on the lunatesurface of the acetabulum, and a sphere is fit to those points using aleast squares calculation. The center of the best fit sphere in patientcoordinates, relative to the center of the pelvic marker, gives thenative center of rotation of the hip (see FIG. 21). The diameter of thesphere could be used to suggest a cup size and reaming sequence to thesurgeon.

In some embodiments, before beginning the cup orientation targeting, orat any other time desired after recording the pelvic marker orientationvectors in patient coordinates, the handheld surgical device may betared to re-establish the handheld surgical device-to-patient adjustmentquaternion, because the axes of the handheld device may drift over timeor the pelvis could move on the operating table. The handheld device canbe engaged with the pelvic marker in a unique orientation, andorientation is recorded (for example, by pressing the set key). Thehandheld-device-to-patient adjustment quatemion may be recalculated byfinding the quaternion rotation from the marker engagement axes inhandheld device coordinates to the marker engagement axes in patientcoordinates (recorded as described herein).

According to some embodiments, the shaft of the handheld surgical toolmay then be fitted with the instrument shaft of a reaming tool or cupimpactor 850 such that the reaming tool or cup impactor is locatedwithin the acetabulum (see FIG. 19B. When the handheld device isengaged, the software will guide the surgeon to hold the cup impactor orreamer in the desired orientation by means of a bullseye targetinginterface (see FIGS. 19C and 22). Once the acetabulum is properlyreamed, a prosthetic cup is implanted therein.

In some embodiments, after the cup is placed in the acetabulum, thesurgeon can adjust the orientation of the cup according to feedback fromthe software as to its location within the impingement-free zone definedby the range of motion model (see FIG. 23). The surgeon can choose adesired orientation, integrating feedback from the range of motion modelwith the patient's specific anatomy.

In some embodiments, after the cup is impacted, a liner is placed intothe cup. In certain embodiments, an appropriately sized trial head isplaced into the liner before scanning, to facilitate detection of thenew center of rotation by a point cloud matching algorithm. In certainembodiments, the center of rotation is detected by scanning the emptyliner and fitting a sphere to points selected on the spherical surfaceof the liner.

As FIG. 24 depicts, a new three-dimensional contour/surface 700 may begenerated, which is based upon image data generated by imaging device500 of the acetabulum, and which includes first marker 601 and theimplanted cup. An updated acetabular plane may then be calculated andmay be displayed in relation to the three-dimensional contour/surface700. Anteversion and inclination of the implanted cup can also becalculated from the three-dimensional contour/surface 700.

In some embodiments, the imaging device 500 may obtain a single pointcloud file in which the pelvic marker, the rim of the implanted cup, andtrial head are visible (see FIG. 25). A point cloud matching algorithmcan be run on the three-dimensional scan to identify the location andorientation of the pelvic marker in scan coordinates, and the locationof the center of rotation relative to the pelvic marker. These valuesare converted to patient coordinates. In certain embodiments, severalpoints are chosen along the rim of the implanted acetabular cup, and theradiographic inclination and anteversion angles of the cup arecalculated from the normal vector to the best-fit plane of those chosenpoints (i.e. the cup axis, {right arrow over (a)}_(cup)). The cup axisis then projected onto the coronal plane (coronal normal vector {rightarrow over (n)}_(coronal)=ĵ) by the following formula:

${\overset{\rightarrow}{a}}_{{cup},{c{oronal}}} = {{\overset{\rightarrow}{a}}_{cup} - {\frac{{\overset{\rightarrow}{a}}_{cup} \cdot \hat{J}}{{{\overset{\rightarrow}{a}}_{cup}}^{2}}{{\overset{\rightarrow}{a}}_{cup}.}}}$

The inclination is calculated as the angle between {right arrow over(a)}_(cup,coronal) and the longitudinal axis of the patient ({circumflexover (k)}):

${{inclination}\left\lbrack \deg \right\rbrack} = {\frac{180}{\pi}{{\cos^{- 1}\left( \frac{{\overset{\rightarrow}{a}}_{{cup},{coronal}} \cdot \overset{\hat{}}{k}}{{{\overset{\rightarrow}{a}}_{{cup},{coronal}}}{\overset{\rightarrow}{k}}} \right)}.}}$

The anteversion is calculated as the angle between the cup axis and itsprojection on the coronal plane:

${{anteversion}\left\lbrack \deg \right\rbrack} = {\frac{180}{\pi}{{\cos^{- 1}\left( \frac{{\overset{\rightarrow}{a}}_{{cup},{coronal}} \cdot {\overset{\rightarrow}{a}}_{cup}}{{{\overset{\rightarrow}{a}}_{{cup},{coronal}}}{{\overset{\rightarrow}{a}}_{cup}}} \right)}.}}$

In other embodiments, the radiographic inclination and anteversionangles of the cup axis are calculated by matching a three-dimensionalmodel of the cup rim with known orientation to the three-dimensionalscan, using a point cloud matching algorithm.

In some embodiments, the femur may be broached prior to acetabular cupplacement. In alternative embodiments, the femur may be broached afteracetabular cup placement.

Once the cup has been implanted and the femur has been resected, a trialstem may be placed into the femur. Based upon the imaging data anddetermined orientations/angles/distances, the system can calculateoptimal prosthetic components, such as optimal stem, head, insert, andadaptor. Imaging device 500 can image the relevant anatomy when thetrial is implanted to test conformity of the prosthetic.

In some embodiments, the imaging device 500 is used to obtain a singlepoint cloud file including both the femoral and pelvic markers. A pointcloud matching algorithm may be run on the three-dimensional scan toidentify the location and orientation of each marker in scancoordinates. Because the pelvic marker orientation is known in patientcoordinates, the quaternion rotation between scan axes and patient axescan be calculated. The orientation vectors of the markers and the vectorconnecting the centers of the two markers are calculated and recorded inpatient coordinates.

Once the final prosthetic is implanted another imaging device 500 canimage the relevant anatomy again to measure the Leg Length Discrepancy(LLD) and Offset and fine-tune the choice of implant's elements toreduce LLD and offset to zero (or to a predefined value).

In some embodiments, the length offset change may be calculated. Thechange in leg offset for the current trial with respect to the nativeoffset is reported in the mediolateral (x), anteroposterior (y), andcraniocaudal (z) directions in the surgical summary display. In order toreliably compare the data between the initial and trial inter-markerscans, the trial leg may be virtually rotated around the trial center ofrotation to match the leg orientation in the initial scan, beforefinding the offset change as the difference between the trial andinitial inter-marker distances. The leg orientation is defined by thefemoral marker orientation. To find the transformation from the trialleg orientation to the initial leg orientation (T_(1,0)), the matrixsystem is solved:

$T_{1\rightarrow 0} = {\begin{bmatrix}a_{0_{x}} & b_{0_{x}} & c_{0_{x}} \\a_{0_{y}} & b_{0_{y}} & c_{0_{x}} \\a_{0_{z}} & b_{0_{z}} & c_{0_{x}}\end{bmatrix}\left( \begin{bmatrix}a_{1_{x}} & b_{1_{x}} & c_{1_{x}} \\a_{1_{y}} & b_{1_{y}} & c_{1_{x}} \\a_{1_{z}} & b_{1_{z}} & c_{1_{x}}\end{bmatrix} \right)^{- 1}}$

Where {right arrow over (a₀)} is the initial femoral marker axis inpatient coordinates, {right arrow over (b₀)} is the initial femoralmarker roll vector in patient coordinates, and {right arrow over(c₀)}={right arrow over (a₀)}×{right arrow over (b₀)}; {right arrow over(a₁)}; is the trial femoral marker axis in patient coordinates, {rightarrow over (b₁)} is the trial femoral marker roll vector in patientcoordinates, and {right arrow over (c₁)}={right arrow over (a₁)}×{rightarrow over (b₁)}. If m_(f) ₁ (x, y, z) is defined as the center of thefemoral marker in patient coordinates as measured in the trial scan, andc₁(x, y, z) as the trial center of rotation in patient coordinates, then{right arrow over (v₁)}=m_(f) ₁ c₁ is the vector pointing from the trialcenter of rotation to the center of the femoral marker as measured inthe trial scan. To adjust the location of the femoral marker in thetrial scan according to the orientation of the leg in the initial scan,m_(f) _(1,adj) , T_(1→0){right arrow over (v₁)}+c₁ is calculated. Thechange in offset is: Δoffset=m_(f) _(1,adj) =m_(f) ₀ .

In some embodiments, a “Position Planning” program may be initiated atthe beginning of the surgery. The Position Planning program requiresinput by the user of one or more of the following: (i) confirmation orchanges to the surgical workflow options; (ii) the cup position-planningmodel; (iii) implants expected to be used in the surgery, in which theirgeometric parameters are automatically inputted into the chosen cupposition model; and (iv) patient's sitting and standing pelvic tilts. Insome embodiments in which the acetabulum is prepared before the femur,the patient's native femoral antetorsion may be inputted to the model,and the implant antetorsion is calculated as the sum of the nativeantetorsion and the designed antetorsion of the chosen stem. In otherembodiments in which the femur is prepared before the acetabulum, thepatient's native femoral antetorsion may not be inputted to the model,and the implant antetorsion is measured by engaging the handheldsurgical tool with the implanted stem. The engagement vector may berecorded in patient coordinates, and the known transformation betweenthe engagement axis and the stem axis may be used to calculate the stemorientation in patient coordinates.

In some embodiments, the LMD may also be used to measure LLD or offset,but to do so, the two markers need to have the same relative orientationbefore and after in order to make the distance measurements comparable.This can be achieved by defining a neutral position, e.g., to reproducethe patient in a standing position by holding the leg up (lateraldecubitus) or by placing the leg parallel to the other one (supine); oralternatively, by using the LMD to navigate accurately the femurorientation. By recording the orientation of the femoral marker beforethe implantation of the prosthesis, the marker engager attached to thehandheld surgical tool can engage the femoral marker again, and then thefemur can be moved until the femoral marker achieves the sameorientation as prior to the implantation.

In certain embodiments, there is an option to save a patient's positionplan, including selection of cup placement model, surgical implantparameters, and patient specific geometric parameters, to a localdatabase. In addition, a randomly generated surgery ID may be assignedto each saved position plan. The position plan will not containpatient-identifying information.

In certain embodiments, a position plan may be selected from a list ofsaved position plans, and either load the data into the GUI module, ortransfer the data to another computer.

Shoulder Arthroplasty

In embodiments of the invention, the surgical navigation system of thepresent invention may be used for performing shoulder arthroplastyincluding, but not limited to, anatomical shoulder arthroplasty, reverseshoulder arthroplasty, tumor shoulder arthroplasty, and revisionshoulder arthroplasty. In particular, the surgical navigation system ofthe present invention may be used to determine correct implantpositioning.

In some embodiments, use of the surgical navigation system for shoulderarthroplasty involves registering the position of the glenoid with thehandheld surgical tool and mapping it to a three-dimensional model. Thisthree-dimensional model is generated from a computerized tomography (CT)scan or a magnetic resonance image (MRI).

In embodiments of the invention, a pre-planning data file may begenerated for use with the shoulder arthroplasty. The pre-planning datafile may contain information including, but not limited to: (i) thethree-dimensional geometry of the patient's operative scapula derivedfrom a CT or MRI scan; (ii) whether the operative scapula is a right ora left scapula; (iii) a three-dimensional point representing a plannedK-Wire entry point in the coordinate system of the three-dimensionalmodel; (iv) a three-dimensional vector representing a planned K-Wiredirection in the coordinate system of the three-dimensional model fromthe planned entry point; (v) a three-dimensional point representing themost superior point on the glenoid in the coordinate system of thethree-dimensional model; (vi) a three-dimensional point representing themost inferior point on the glenoid in the coordinate system of thethree-dimensional model; (vii) a three-dimensional point representingthe most posterior point on the glenoid in the coordinate system of thethree-dimensional model; (viii) a three-dimensional point representingthe most anterior point on the glenoid in the coordinate system of thethree-dimensional model; and/or (ix) a three-dimensional pointrepresenting the center point of the glenoid in the coordinate system ofthe three-dimensional model. In some embodiments, the anterior,posterior, superior, inferior, and center points of the glenoid shall bechosen algorithmically.

Prior to the surgery, the pre-planning data file shall be imported intothe GUI module for annotation of the patient's three-dimensional scapulamodel. During the annotation process, information extracted from thethree-dimensional model may be used to register the intraoperativeorientation of the patient's glenoid, and thereby map the pre-plannedk-wire orientation onto the patient's real glenoid.

In some embodiments, the scapular model shall be displayed in the GUImodule, along with the points described as being in the pre-planningdata file. The user may have the opportunity to confirm or re-do theselection of these points, but not the k-wire direction and entry point.

To set up for surgery, the handheld surgical tool is initialized, i.e.,it measures the direction of gravity and orients its axes such that itsY-axis points opposite to gravity. The operative shoulder may then beexposed, and soft tissues are removed that are not visible on thethree-dimensional model. The K-Wire insertion position may be marked onthe glenoid using electrocautery.

In some embodiments, a marker may be installed on the scapula. Themarker may be able to engage with the handheld surgical tool in a manneraccording to embodiments of the invention, to allow the orientation ofthe marker to be recorded.

In some embodiments, the glenoid may be scanned using the 3D scanner,such that physical attributes of the glenoid may be identified insteadof markers.

On the visual display, a three-dimensional model of the patient'sglenoid may be displayed.

After the transformation between the handheld surgical tool and glenoidcoordinate, the GUI module can display a three-dimensional animationdepicting the real-time computed orientation of the handheld surgicaltool with attached tool in relation to the patient's glenoid. As theuser moves the tool, the user can confirm that the orientation andmotion of the tool relative to the patient's glenoid scan in thethree-dimensional animation matches the orientation and motion of thetool relative to the patient's actual glenoid on the operating table.

In some embodiments, the transformation between the handheld surgicaltool and glenoid coordinate system may be computed by means of a contourtracing. In such embodiments, a jig that interfaces with the handheldsurgical tool may be installed on the glenoid. The handheld surgicaltool can be traced along the surface of the glenoid, and thetransformation shall be calculated by matching the recorded contour tothe expected one.

In some embodiments, the orientation of a marker installed on thescapula can be recorded by engaging with the handheld surgical tool.Subsequent re-engagement with the scapula marker can allow for arecalculation of the transformation between the handheld surgical tooland the glenoid coordinate systems, thereby eliminating accumulatederrors including, but not limited to, errors due to gyroscope drift, andmobility of the patient's scapula.

In some embodiments, distances in the shoulder may be measured with ascanner or LMD as described for the hip arthroplasty. Similarly, centerof rotation may be measured for the shoulder as described for the hiparthroplasty.

In embodiments in which a K-Wire is used for the shoulder arthroplasty,a K-Wire Guide 975 as shown in FIG. 26 may be attached to the handheldsurgical tool 200. The user can insert the K-Wire 980 into the K-WireGuide 975 and position the K-Wire 980 on the K-Wire insertion point 990.The visual display 410 can display an animation of the real-time K-WireGuide 975 position relative to the patient's glenoid 875, and adepiction of the desired K-Wire trajectory. The user can also utilizefeedback from the animation to move the K-Wire Guide 975 into thecorrect trajectory. The GUI module can indicate, for example by sound orcolor or other graphical means, when the K-Wire Guide 975 is being heldwithin a predefined angular tolerance from the desired trajectory (seeFIGS. 27A and 27B). The user can drill the K-Wire into the patient'sglenoid 875 while the K-Wire Guide 975 is being held in the correcttrajectory as indicated by the GUI module (see FIG. 27).

The above-described systems and methods are given for clearness ofunderstanding only, and alternative computer-aided surgical navigationsystems and methods are within the scope of this disclosure. Forexample, the systems and methods may be carried out for surgicalprocedures besides the illustrated hip arthroplasty and shoulderarthroplasty procedures.

Detailed embodiments of the present systems and methods are disclosedherein; however, it is to be understood that the disclosed embodimentsare merely illustrative and that the systems and methods may be embodiedin various forms. In addition, each of the examples given in connectionwith the various embodiments of the systems and methods are intended tobe illustrative, and not restrictive.

Throughout this specification and the claims which follow, unless thecontext requires otherwise, the word “comprise” and variations such as“comprises” and “comprising” will be understood to imply the inclusionof a stated integer or step or group of integers or steps but not theexclusion of any other integer or step or group of integers or steps.

Throughout the specification, where systems are described as includingcomponents, it is contemplated that the compositions can also consistessentially of, or consist of, any combination of the recited componentsor materials, unless described otherwise. Likewise, where methods aredescribed as including particular steps, it is contemplated that themethods can also consist essentially of, or consist of, any combinationof the recited steps, unless described otherwise. The inventionillustratively disclosed herein suitably may be practiced in the absenceof any element or step which is not specifically disclosed herein.

The practice of a method disclosed herein, and individual steps thereof,can be performed manually and/or with the aid of or automation providedby electronic equipment. Although processes have been described withreference to particular embodiments, a person of ordinary skill in theart will readily appreciate that other ways of performing the actsassociated with the methods may be used. For example, the order ofvarious steps may be changed without departing from the scope or spiritof the method, unless described otherwise. In addition, some of theindividual steps can be combined, omitted, or further subdivided intoadditional steps.

All patents, publications and references cited herein are hereby fullyincorporated by reference. In case of conflict between the presentdisclosure and incorporated patents, publications and references, thepresent disclosure should control.

What is claimed is:
 1. A surgical navigation system for use in apatient, the surgical navigation device comprising: a handheld surgicaltool with computer-aided navigation, wherein the handheld surgical toolcomprises a handle and an instrument shaft; a graphical user interface(GUI) module, wherein the GUI module comprises a computing device and avisual display that is configured to display an indications of alocation of the handheld surgical tool; and an imaging device.
 2. Thesurgical navigation system of claim 1, wherein the handle includes aprocessor and a sensor unit.
 3. The surgical navigation system of claim2, wherein the sensor unit comprises a 3-axis accelerometer, a 3-axisrate gyroscope, a 3-axis magnetometer, or a combination thereof
 4. Thesurgical navigation system of claim 2, wherein the sensor unit isconfigured to generate orientational data of the handheld surgical tool.5. The surgical navigation system of claim 4, wherein the processor orthe computing device is configured to determine the orientation of thehandheld surgical tool based on the orientational data.
 6. The surgicalnavigation system of claim 5, wherein the processor or the computingdevice is configured to compare the orientation of handheld surgicaltool with at least one preset target orientation and the visual displayis configured to indicate deviation of the orientation of the handheldsurgical tool from the at least one preset target orientation.
 7. Thesurgical navigation system of claim 1, wherein the imaging device isconfigured to generate a three-dimensional image or contour of a surfaceof the patient's anatomy or portion thereof for display in conjunctionwith the indication of the location of the handheld surgical tool. 8.The surgical navigation system of claim 7, wherein the three-dimensionalmodel or contour of the surface of the patient's anatomy or portionthereof is generated based upon data from the imaging device.
 9. Thesurgical navigation system of claim 1, wherein the imaging devicecomprises a time-of-flight camera, a pair of stereoscopic cameras, or athree-dimensional scanning tool.
 10. The surgical navigation system ofclaim 1, further comprising a marker that is attachable to a portion ofthe patient's anatomy.
 11. The surgical navigation system of claim 10,further comprising a marker engager attached to the handheld surgicaltool, the marker engager being configured to engage with the marker at aset orientation.
 12. The surgical navigation system of claim 10, whereinthe processor or the computing device is configured to detect anorientation of the marker.
 13. The surgical navigation system of claim10, wherein a processor or the computing device is configured to measureangular orientations and linear distances of anatomical features inrelation to the marker.
 14. The surgical navigation system of claim 1,wherein the GUI module is configured to receive data on one or more oflocation of the handheld surgical tool, deviation of the location of thehandheld surgical tools from a desired location for the handheldsurgical tool, images of the patient's anatomy or a portion thereof, anda three-dimensional model of the patient's anatomy or a portion thereof15. The surgical navigation system of claim 14, wherein the GUI moduleis configured to overlay one or more of: the images of the patient'sanatomy or a portion thereof, the three-dimensional model of thepatient's anatomy or a portion thereof, the location of the handheldsurgical tool, and an indication of the desired location for thehandheld surgical tool.
 16. The surgical navigation system of claim 15,wherein the indication includes at least one of: a visual indication, atactile indication, or an aural indication.
 17. A method of implanting aprosthesis in patient undergoing a joint arthroplasty using a surgicalnavigation system, wherein the surgical navigation system comprises: ahandheld surgical tool with computer-aided navigation, wherein thehandheld surgical tool comprises a handle and an instrument shaft; agraphical user interface (GUI) module executed by a computing device,wherein the GUI module comprises a visual display that is configured toindicate the location of the handheld surgical tool; and an imagingdevice; the method comprising: exposing the joint of the jointarthroplasty; placing one or more markers on anatomical features of thejoint; engaging the handheld surgical tool with the one or more markersand recording orientation of the handheld surgical tool during theengagement; registering the orientation of the handheld surgical toolrelative to the orientation of the joint; displaying the orientation ofthe handheld surgical tool and a predetermined target orientation forthe handheld surgical tool, on the visual display; and implanting theprosthesis using the handheld surgical tool and the visual display,wherein the orientation of the handheld surgical tool is adjustedaccording to the predetermined target orientation for the handheldsurgical tool.
 18. A method of implanting a prosthesis in patientundergoing a joint arthroplasty using a surgical navigation system,wherein the surgical navigation system comprises: a handheld surgicaltool with computer-aided navigation, wherein the handheld surgical toolcomprises a handle and an instrument shaft; a graphical user interface(GUI) module executed by a computing device, wherein the GUI modulecomprises a computing device and a visual display that is configured toindicate the location of the handheld surgical tool; and an imagingdevice; the method comprising: exposing the joint of the jointarthroplasty; recording an image data of the anatomy of the joint, or aportion thereof, using the imaging device; generating athree-dimensional image or contour of the anatomy of the joint, or theportion thereof, using the GUI module; engaging the handheld surgicaltool with the one or more anatomic features on the joint and recordingorientation of the handheld surgical tool during the engagement;registering the orientation of the handheld surgical tool relative tothe orientation of the joint; displaying one or more of thethree-dimension image or contour, the orientation of the handheldsurgical tool, and a predetermined target orientation for the handheldsurgical tool, on the visual display; and implanting the prosthesisusing the handheld surgical tool and the visual display, wherein theorientation of the handheld surgical tool is adjusted according to thepredetermined target orientation for the handheld surgical tool.
 19. Themethod of claim 18, wherein the handle comprises a processor and asensor unit.
 20. The method of claim 19, wherein the sensor unitcomprises a 3-axis accelerometer, a 3-axis rate gyroscope, a 3-axismagnetometer, or a combination thereof
 21. The method of 19, wherein thesensor unit is configured to generate orientational data of the handheldsurgical tool, and the processor or the computing device is configuredto determine, based on the orientational data, the orientation of thehandheld surgical tool and compare the orientation of handheld surgicaltool with at least one preset target orientation.
 22. The method ofclaim 21, wherein the visual display is configured to indicate adeviation of the orientation of the handheld surgical tool from the atleast one preset target orientation.
 23. The method of claim 18, furthercomprising generating a three-dimensional image or contour of a surfaceof the patient's anatomy or portion thereof for display in conjunctionwith the indication of the location of the handheld surgical tool. 24.The method of claim 18, wherein the joint arthroplasty is a hiparthroplasty, knee arthroplasty, or shoulder arthroplasty.